• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.795-798
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• 2002

In this investigation, experimental attempts were made to observe and determine the variations in elastic of the PVC depending on the amounts of MBS added to the mixture, PVC/MBS, and also on the thicknesses of the specimens. An acoustic resonance technique was used for the tests in this investigation. It serves as a method to characterize properties of materials set in vibrational motions, which is initiated by low level stresses generated by externally supplied acoustic energy. Substantial variations were observed in the test results with the addition of the MBS to the PVC. It was found that the magnitudes of elastic constants decrease when MBS rubber was added in the range up to 9 phr and the shape factor effect in torsional vibration is more significant than the shape factor effect in flexural vibration.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.353-356
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• 2002

Planar laser induced fluorescence(PLIF) has been widely used to obtain two dimensional fuel distribution. Preliminary investigation was performed to measure quantitative air excess ratio distribution in an engine fueled with LPG. It is known that fluorescence signal from acetone as a fluorescent tracer is less sensitive to oxygen quenching than other dopants. Acetone was excited by KrF excimer laser (248nm) and its fluorescence image was acquired by ICCD camera with a cut-of filter to suppress Mie scattering from the laser light. For the purpose of quantifying PLIF signal, an image processing method including the correction of laser sheet beam profile was suggested. Raw images were divided by each intensity of laser energy and profile of laser sheet beam. Inhomogeneous fluorescence images scaled with the reference data, which was taken by a calibration process, were converted to air excess ratio distribution. This investigation showed instantaneous quantitative measurement of planar air excess ratio distribution for gaseous fuel.

• Interaction and multiscale mechanics
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• v.5 no.2
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• pp.115-129
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• 2012

Nanowires (NWs) have attracted intensive researches owing to the broad applications that arise from their remarkable properties. Over the last decade, immense numerical studies have been conducted for the numerical investigation of mechanical properties of NWs. Among these numerical simulations, the molecular dynamics (MD) plays a key role. Herein we present a brief review on the current state of the MD investigation of nanowires. Emphasis will be placed on the FCC metal NWs, especially the Cu NWs. MD investigations of perfect NWs' mechanical properties under different deformation conditions including tension, compression, torsion and bending are firstly revisited. Following in succession, the studies for defected NWs including the defects of twin boundaries (TBs) and pre-existing defects are discussed. The different deformation mechanism incurred by the presentation of defects is explored and discussed. This review reveals that the numerical simulation is an important tool to investigate the properties of NWs. However, the substantial gaps between the experimental measurements and MD results suggest the urgent need of multi-scale simulation technique.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.6
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• pp.571-578
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• 2012

In this paper, an experimental investigation is performed to estimate the thermal performance of a natural convective heat sink with plate fins subject to the uniform wall temperature condition. Extensive experiments are performed with various input powers, fin spacings, and heights of the natural convective heat sinks with plate fins. In particular, the effect of the inclination angle on the thermal performance of the heat sink is studied. In order to validate the experimental data, the experimental results are compared with results from previous studies. Based on the experimental results, the appropriate ranges of the previous correlations between the input power, the fin spacing, the fin height, and the inclination angle for the natural convective heat sink with plate fins are evaluated.

• Structural Engineering and Mechanics
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• v.49 no.5
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• pp.555-568
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• 2014

In this article, stability of composite conical shells subjected to dynamic external pressure is investigated by numerical and experimental methods. In experimental tests, cross-ply glass woven fabrics were selected for manufacturing of specimens. Hand-layup method was employed for fabricating the glass-epoxy composite shells. A test-setup that includes pressure vessel and data acquisition system was designed. Also, numerical analyses are performed. In these analyses, effect of actual geometrical imperfections of experimental specimens on the numerical results is investigated. For introducing the imperfections to the numerical models, linear eigen-value buckling analyses were employed. The buckling modes are multiplied by very small numbers that are derived from measurement of actual specimens. Finally, results are compared together while a good agreement between results of imperfect numerical analyses and experimental tests is observed.

• Computers and Concrete
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• v.1 no.3
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• pp.227-248
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• 2004

A combined experimental-computational study of a double edge-notched stone specimen subjected to tensile loading is presented. In the experimental part, the load-deformation response and the displacement field around the crack tip are recorded. An Electronic Speckle Pattern Interferometer (ESPI) is used to obtain the local displacement field. The experimental results are used to validate a numerical model for the description of fracture using finite elements. The numerical model uses displacement discontinuities to model cracks. At the discontinuity, a plasticity-based cohesive zone model is applied for monotonic loading and a combined damage-plasticity cohesive zone model is used for cyclic loading. Both local and global results from the numerical simulations are compared with experimental data. It is shown that local measurements add important information for the validation of the numerical model. Consequently, the numerical models are enhanced in order to correctly capture the experimentally observed behaviour.

• Korean Journal of Child Studies
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• v.12 no.2
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• pp.67-77
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• 1991

An investigation of the effect of occupational information on vocational cognitive complexity was conducted with 331 male and female adolescents in ninth grade. There were 2 experimental groups and 1 control group. Experimental group I was given only occupational information sheets (written form information) while group II was given occupational information through verbal instruction in addition to the occupational information sheets. A modified form of the cognitive complexity grid originally developed by Bodden (1970) was utilized to collect data on the subjects' vocational cognitive complexity. ANOVA and $Scheff{\acute{e}}$ tests revealed that there were significant differences between experimental group II and the other groups in vocational cognitive complexity. The cognitive complexity level of experimental group I and the control group for the most aspired occupation was significantly lower than for the least aspired occupation. However, the cognitive complexity level of experimental group II for the most aspired occupation was higher than for the least aspired occupation. The results suggest that just giving occupational information to adolescents may not be effective and giving occupational information may be effective only when the method of giving occupational information is active enough to induce adolescents' self-confirming cognitive process.

• International Journal of Concrete Structures and Materials
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• v.7 no.4
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• pp.273-285
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• 2013

An experimental investigation was conducted to compare the shear strength of full-scale beams constructed with chemically-based, self-consolidating concrete (SCC) with conventional concrete (CC). This experimental program consisted of 16 rectangular beams (12 without shear reinforcing and 4 with shear reinforcing in the form of stirrups), 8 beams for each mix design. Additionally, three different longitudinal reinforcement ratios were evaluated within the test matrix. The beam specimens were tested under a simply supported four-point condition. The experimental shear strengths of the beams were compared with both the shear provisions of selected standards (U.S., Australia, Canada, Europe, and Japan) and a shear database of CC specimens. This comparison indicates that chemically-based SCC beams possess comparable shear strength as CC beams.

• Steel and Composite Structures
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• v.24 no.4
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• pp.383-390
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• 2017

This paper highlights the experimental and numerical investigations performed on a tubular T-joint fabricated from circular hollow sections under axial compressive loads applied at the brace. Tests were performed on a reference joint and the joint wrapped with Carbon Fiber Reinforced Polymer (CFRP). The Nitowrap EP carbon fiber with Nitowrap 410 resin serve as a composite material is used for wrapping the T-joint. Schematic diagram of the fabricated tubular joint for the experimental test setup, along with the experimental and numerical results are presented. After performing these experiments, it has been demonstrated that the joint wrapped with CFRP has a better strength and lesser deflection than a reference joint. Finite element analysis carried out in Ansys reveals that the results were in good correlation with the experimental values.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2005.05a
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• pp.288-293
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• 2005

A earn profile grinding machine is a mandatory machine tool for manufacture of high precision contoured cam. Experimental evaluation of modal analysis is an effective tool to investigate dynamic behavior of a machine. This paper presents the measurement system and experimental investigation on the modal analysis of a grinding machine. The weak part of the machine is found by the experimental evaluation. The results provide structure modification data for good dynamic behaviors. And safety of the machine was confirmed by the modal analysis of modified machine design. Finally, the cam profile grinding machine was successfully developed.